WO1998013147A1

WO1998013147A1 - Sublimation dye transfer compositions and methods

Info

Publication number: WO1998013147A1
Application number: PCT/US1997/017249
Authority: WO
Inventors: Vaughn Barnes; Robert David; David Janes
Original assignee: California Manufacturing Enterprises
Priority date: 1996-09-26
Filing date: 1997-09-25
Publication date: 1998-04-02
Also published as: AU4652197A

Abstract

A metallic or other deformable surface is coated with a highly cross-linked polymer having a hardness greater than 80 (Shore D, ASTM D2240) and a coefficient of elasticity of at least 120 % without breaking, the coating is cured, and an image is sublimated into the coating. In preferred embodiments the polymer is cured using ultraviolet (UV) light, and is sprayed onto the surface using a substantially solvent free mixture. In other aspects the polymeric coating comprises at least one of polymerizable acrylate, a polyurethane and especially a polycarbonate urethane or a cycloaliphatic urethane, and a peracid epoxy.

Description

SUBLIMATION DYE TRANSFER COMPOSITIONS AND METHODS

Field of The Invention

This invention relates to decoration of polymer coated surfaces.

Background of The Invention

Decoration of manufactured articles has been undertaken for many centuries. In its simplest forms such decorations include painting of ceramic vessels, furniture and other household items, and dying of fabrics. In more sophisticated forms the decorations may include photographic quality images on papers, laminates and the like.

Complex images and patterns can be placed on objects using many different technologies, including silk screening and sublimation transfers. In sublimation transfers, one or more dyes are printed onto a transfer medium such as paper or cloth, and the transfer medium is juxtaposed against the surface(s) of the substrate being decorated. Heat and/or pressure are then usually applied such that the dyes are transferred to the receiving surface.

Sublimation dye processing has been notoriously difficult to achieve with some classes of materials. Many plastics, for example, have a tendency to stick to the transfer paper, requiring an intermediate sheet or other special processing to effect the process. (See, e.g., US 3,952, 131 to Siderman (4/76) and US 4,059,471 to Haigh (11/77)). Metals have a different problem, in that the molecular structure is generally not sufficiently porous^ø accept the dyes. Wood has still another problem. Woods and elastomeric substances such as foams and rubbers usually receive the dyes well, but then allow them to "bleed" throughout the cellulose structure.

Some of these problems can be resolved by coating the substrate with a polymer, and then sublimating the dyes into the coating. US 5,142,722 to Kolb (9/92), for example, describes application of a polyester base coat to wooden furniture end pieces, and then sublimating an image or other pattern onto the polyester. Similarly, US 5,523,273 to McQuaide (6/96) describes application of a barrier layer followed by successive polymeric coatings onto foamed and elastomeric substrates, and then sublimating the dyes into the various coatings. As another example, US 5,234,983 to Valenty (10/93) describes coating coffee mugs with a polyurethane base comprising a mixture of epoxy resin and blocked polyisocyante.

Such techniques, however, do not work well with all surfaces. One problem with metallic surfaces, for example, is that metals tend to bond poorly to polymers. Another problem is that metals and polymers tend to have quite different coefficients of thermal expansion. These and other factors can result in chipping, flaking and peeling of the polymer coatings. The problems are particularly severe where the coated object s subjected to high temperature swings, as in the case of guard rails or residential down spouts.

Other problems arise where the coated object is subject to physical deformation. Coatings on metal baseball bats, for example, must be relatively hard to withstand impact of baseballs, and yet flexible enough to both deform and then recover from deformation caused by the impact.

Similarly, coatings on tennis racquets and golf clubs need to be hard enough to withstand scratching and other surface damage, but must be able to withstand considerable bending during use. In all these cases cracking, chipping, peeling and other instabilities of hard coatings is expected, and there is certainly no reason to place sublimate images into the coating. The US 5,523,273 patent, for example, describes sublimating dyes into a flexible polymer which could be applied to metallic surfaces, but the polymer has a Shore D hardness of only about 30 to about 70.

Still other problems arise from application factors associated with depositing polymeric coatings. Volatile organic solvents, for example, are to be generally avoided because can create health hazards to employees who are chronically exposed t» the fumes thereof, including ocular, pulmonary, renal and integument problems.

Thus, there remains a need for compositions and methods which provide high quality imaging on metal and other surfaces subject to significant deformation, while retaining sufficient hardness and wear resistance. In addition, there is a need to accomplish these goals using coating compositions which have desirable application characteristics such as minimal use of volatile components, good adhesion and setting characteristics. Summary of the Invention

It has now been discovered that polymers meeting a combination of criteria can be successfully used to coat metallic surfaces, and can receive and retain high quality sublimation images. In preferred embodiments a metallic surface is coated with a highly cross-linked polymer having a hardness greater than 80 (Shore D, ASTM D2240) and a coefficient of elasticity of at least 120% without breaking, the coating is cured, and an image is sublimated into the coating. In particularly preferred embodiments the coating is formulated using one or more acrylates and one or more photoinitiators. In another aspects of preferred embodiments, the coating is applied as a substantially solvent free mixture.

Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.

Detailed Description of Preferred Embodiments

Preferred embodiments herein generally comprise coating a metallic or other deformable surface with a highly cross-linked polymer having a hardness greater than 80 (Shore D, ASTM D2240) and a coefficient of elasticity of at least 120% without breaking, the coating is cured, and an image is sublimated into the coating. As used herein, the term "image" is used in a generic sense to include any visually identifiable pattern, including all manner of photographs, pictures, drawings, line art, logos, words, non-geometric patterns such as wood grains, geometric patterns, mono-colors, pigments, shading, and so forth, regardless of whether or not colors are involved.

Considering first the objects and surfaces to be coated, it is contemplated that such objects and surfaces are those which may be subjected to substantial deformation. The deformation may be due to any cause, including thermal effects such as expansion or contraction, and mechanical effects such as shearing, torquing or bending. In addition, the deformation may or may not be completely elastic. One exemplary class of substrate materials contemplated herein comprise metallic surfaces, the terms "metal" and "metallic" being used generically to include pure metals, alloys, composites and other metallic compositions. Other exemplary classes of substrate materials include structural plastics. Contemplated applications thus include sporting equipment such as snow and water skis, skiing or high jumping poles, metal baseball and softball bats, shafts and heads of golf clubs. Other contemplated applications include building materials such as plastic siding, window mouldings, piping, water faucets, guard rails and downspouts.

Still other contemplated applications include metallic and composite furniture, automotive components such as hub caps, rims, and gas tanks, transport devices such as dollies, forklifts and gurneys, and miscellaneous items from metal clad writing pens to planters.

It is contemplated that the relevant surface(s) of objects may be prepared prior to application of the coating or coatings. Suitable surface preparation may include cleaning a bonding area with a solvent or ultrasonic treatment, or roughening the bonding area with an abrasive. Additionally or alternatively, the relevant surface(s) of objects may be prepared prior to application of the coating or coatings by depositing a primer or base coat, which may or may not be a polymer, and which may or may not be pigmented.

Turning to the coating, it is contemplated that such coatings may comprise polymeric compounds discussed in US 5,453,451 to Sokol (9/95). Such coatings have about 80 to about 99.5 weight percent of a polymerizable acrylate, and from about 0.5 to about 15 weight percent of a photoinitiator which initiates a polymerization reaction in the composition when it is exposed to ultraviolet light. More preferably, the composition hereof includes from about 90 to 99.5 percent of the polymerizable compound and from about 0.5 to about 8 percent of the photoinitiator. In particularly preferred embodiments the coating comprises 68 to 84 percent of a first diacrylate, 15 to 25 percent of a second diacrylate, and 1 to 8 percent of the photoinitiator. In this class of coatings, the polymerizable compound may be selected from the group consisting of monoacrylates, diacrylates, triacrylates, urethane-modified acrylates, polyester-modified acrylates and mixtures thereof, with the mixtures being preferred. Suitable acrylates which may be used include trimethylolpropane triacrylate, 1,6 hexane diol diacrylate, aliphatic urethane acrylates, vinyl acrylates, epoxy acrylates, ethoxylated bisphenol A diacrylates, trifunctional acrylic ester unsaturated cyclic diones, polyester diacrylates, and mixtures of the above compositions.

As used herein, the terms "polymer" and "polymeric" refer generically to giant- or macro- molecules, whether crystalline or non-crystalline, derived from a single type of monomer (homo- polymers) or from multiple monomers (co-polymers), whether branched or unbranched, whether inherently cross-linked or chain polymerized, and whether produced by condensation polymerization, emulsion polymerization or otherwise. These terms also include mixtures of giant- or macro-molecules and extenders such as silicates and sulfates, additives such as antifoaming agents, antifouling agents, antioxidants, antisettling agents, curing agents, dispersants, emulsifiers, flatting agents, gloss control agents and heat stabilizers, viscosity control agents, and plasticisers. Such additives are described in Seymour and Mark, Handbook of Organic Coatings. Extenders and other Additives, pp 93-114; Solvents, Plasticizers and Coalescent Solvents, pg 1 19 (Elsevier 1990).

As used herein the term "highly-cross linked" refers to cross-linking which produces average polymeric molecular weights in excess of 10,000. This number, however, is somewhat arbitrary, and various aspects of the inventive subject matter may properly relate to polymers in which the average polymeric molecular weights are greater than 5,000, 25,000, 50,000, 100,000, 250,000 and 500,000.

As disclosed in the US 5,453,451 patent, there are many suitable photoinitiators, including those of the free radical or cationic types. A combination of photoinitiators may also be used. Suitable photoinitiators include l-phenyl-2-hydroxy-2-methyl-l-propanone, oligo{2 hydroxy-2 methyl-l-[4-(methylvinyl)phenyl]propanone}, 2 hydroxy 2-methyl l-phenyl propan-1-one, 1- hydroxycyclohexyl phenyl ketone and benzophenone as well as mixtures thereof. Curing may take place by natural sunlight, by medium pressure mercury arc lights, or by long wave ultraviolet light depending on the photoinitiator package used.

Contemplated coatings herein may or may not be clear. A preferred clear coat composition hereof comprises 65 to 85 percent ethoxylated bisphenol A diacrylate, 15 to 25 percent 1,6 hexanediol diacrylate, and 1 to 8 percent of a photoinitiator which is a mixture of oligo {2-hydroxy-2 methyl- l-[4(methylvinyl)phenyl] propfcnone} and 2-hydroxy-2methyl-l phenyl propan-1-one, sold commercially by Sartomer, Inc. under the mark ESACURE™ KP100F. A preferred pigmented formula in accordance with the present invention comprises 60 to 80 percent ethyoxylated bisphenol A diacrylate, 15 to 25 percent 1,6-hexanediol diacrylate, 0.1 to 10 percent pigment solids, and 1 to 8 percent of a photoinitiator which is a mixture of oligo {2-hydroxy-2 methyl- l-[4(methylvinyl)phenyl] propanone) and 2-hydroxy-2methyl-lphenyl propan-1-one, sold commercially by Sartomer, Inc. under the Mark ESACURE KP100F.

It should also be appreciated that the terms "coating" or "coatings" are used in a broad, generic sense. As such, these terms include composite materials formed at the surface of an object from both the material of the object itself, and from an external component. Such technology was described in US 4,212928 to Arney, Jr. (7/80).

Other coatings are also contemplated, including free radical acrylated urethanes such as Ultra- Violet Coating Ltd. 915-21. This coating is satisfactory provided the surface being coated is thoroughly cleaned to enhance bonding, and ultrasonic cleaning is preferred for this purpose. Other contemplated coatings include polycarbonate urethanes such as Duracarb™ 120 based on straight chain aliphatic diols, and Duracarb ™ 140 based on cycloaliphatic diols, both from PPG Industries Specialty Products Unit in Chicago, Illinois, USA. Still other cycloaliphatic-based polymers are contemplated due to their higher cross-link densities. Examples include the peracid epoxies such as epoxies resulting from perbenzoic acid and olefin. Atypical such resin is vinylcyclohexane dioxide. Still further it is contemplated, as discussed in Goodman, Handbook of

Thermoset Plastics. Peracid Resins, page 137, (Noyes Publications 1991), that peracid based resins including acyclic aliphatic resins such as epoxidized soya or linseed oils, polyglycols and/or polybutadiene, can be used to modify stand resin systems to alter flexibility.

Application of coatings can be performed in many ways, but is preferably performed by spray coating or powder coating. Presently preferred spray equipment is a Ransburg™ "Aerobell

33" rotary atomizing electrostatic bell. Viscosity for spray applications is preferably about 200 CPS, 23 s Zahn #3 at 22° C (72°F). Thickness of dried film coatings is preferably about 500 microns (2-3 mils), but can range between about 25 and about 1000 microns. Powder coatings can be applied by known methods, (see e.g. Satas, Coatings Technology Handbook, pp 37-371 (Marcel Dekker, Inc., 1991), including fluidized bed coating in which finely divided coating material is aerated and deposited on heated articles in a closed container. It is contemplated that the coated objects may be cooled and then reheated in order to obtain more uniform coating. Large articles may be coated using an electrostatic fluidized bed process.

Curing of the coatings can also be performed in many ways. Photoinitiation is contemplated as discussed above, as is electron beam initiation and other technologies.

Photoinitiation, however, is presently preferred because of its convenience and relatively low cost. Where UV light provides the driving force, a production line may, for example, advantageously include an array of Fusion™ F600 microwave generated UV plasma lamps.

Desirable characteristics for the coatings include the following: 1 Conical Mandrel Bend ASTM D 522 1 " diameter with no visible cracking

2. Chipping resistance ASTM D 3170 ≥ 10 chips of 1 mm diameter/sq. inch (stones sorted by 3/8" screen)

3. Cross-Hatch and Tape Pull ASTM D 3359(B) 5B-0% removed

4. Pencil Hardness ASTM D 3363 6H gouge; 4H mar

5 MEK Rubs ASTM D 4752 40 double rubs with no softening of coating using cheese cloth on 21b (1kg) ball peen hammer; 2000 hours

6. QUVB 313 ASTM D 4587 ->50% gloss retained, 1200 hours

7. WeatherOmeter QUVA SAE J1960 ≥ 90% gloss retained, 1200 hours

8. Visual Requirements Gloss/Haze/Distinctiveness subjectively determined of image

9 Elasticity (Flexibility) elongation ≥ 120% without breaking

There is also some leeway in the use of different tests or scales to determine the underlying qualities. For example, the quality of hardness may be variously measured using many different scales, including scratch hardness, file test hardness, Brinell hardness, Vickers hardness and Shore hardness (See Parker, McGraw Hill Encyclopedia of Engineering, Hardness Scales, pp 516-518 (McGraw Hill 1992). Thus, although the above parameters are valid as desirable characteristics, it is also the case that embodiments of the present subject matter may provide polymers having a hardness greater than 80 on the Shore D, ASTM D2240 test.

There is also some leeway in applying these parameters. For example, in various aspects of the present subject matter, contemplated polymers may have hardness as low as 60 or 70, or as high as 90, 100, 110, 120 or more on the Shore D, ASTM D2240 test. Hardness can be varied by methods known to those skilled in the art, including polymerization enhancers or poisons. As another example, while elasticity of at least 120% without breaking is considered highly desirable, greater elasticities of 130%, 150% or more may be more desirable, and lesser elasticities of 115%), 100%) may also be satisfactory.

Thus, specific embodiments and applications have been disclosed which provide stable, high quality sublimation images on objects which may be subject to significant deformation during use. It should be apparent to those skilled in the art, however, that many more modifications besides those already described are possible without departing from the inventive concepts herein The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A method of imparting an image to a metallic surface comprising, providing the surface with a bonding area; coating the bonding area with a highly cross-linked polymer having a hardness greater than 80 (Shore D, ASTM D2240) and a coefficient of elasticity of at least 120% without breaking; curing the polymeric coating; and sublimating dyes characterizing the image into the coating.

2. The method of claim 1 further comprising curing the polymeric coating using ultraviolet

(UV) light.

3. The method of claim 1 wherein the metallic surface comprises a portion of a piece of athletic equipment.

4. The method of claim 3 wherein the athletic equipment comprises a baseball bat.

5. The method of claim 1 wherein the step of coating comprises spraying the polymer on the surface.

6. The method of claim 5 wherein the step of spraying comprises spraying the polymer on the surface using a substantially solvent free mixture.

7. The method of claim 5 wherein the step of spraying comprises powder coating the polymer on the surface.

8. The method of claim 1 further comprising curing the polymeric coating using ultraviolet (UV) light, and spraying the polymer on the surface using a substantially solvent free mixture.

9 The method of claim 1 wherein the cured polymer is substantially transparent.

10 The method of any one of claims 1 - 9 wherein the polymeric coating comprises polymerizable acrylate

1 1. The method of any one of claims 1 - 9 wherein the polymeric coating comprises a polyurethane

12. The method of any one of claims 1 - 9 wherein the polymeric coating comprises a polycarbonate.

13 The method of any one of claims 1 - 9 wherein the polymeric coating comprises a cycloaliphatic urethane.

14. The method of any one of claims 1 - 9 wherein the polymeric coating comprises a peracid epoxy.